I think 2 great areas of research in PL are:

1. Program synthesis. Roughly, deep learning to write code (https://sunblaze-ucb.github.io/program-synthesis/index.html) (tab-9 being an incredible application of it)

2. My own area of research: Tree Notation (https://treenotation.org/). More generally: the idea of programming languages and programs as 2-D and 3-D structures.

I follow thousands of languages and those are the 2 domains that I think are most exciting (I'm obviously biased).

There's lots of incredibly value incremental work as well, but not much else I see that will cause a 10x+ jump.

If you are interested in PL research, I recommend https://reddit.com/r/programmingLanguages and https://futureofcoding.slack.com/